platform: starfive: add PMIC power ops in JH7110 visionfive2 board

add reboot and poweroff support. The whole reboot and shutdown
pm op includes shutdown jh7110 pmu device power domain
and access on board pmic register through I2C.

Signed-off-by: Minda Chen <minda.chen@starfivetech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>